It is always a good idea to hire an attorney. That being said, you have to make a cost benefit analysis. You might want to go to your first court date and try to speak with the prosecutor and explain that due to traffic conditions you were not able to move over. See if the prosecutor might be willing to change the charge to a non-moving violation or something that will not go on your drivers license history. If the prosecutor is unwilling to change the charge you can always request to have your case continued in order to speak with an attorney.
While an attorey might help present your defense, it is unlikely that the cost would be worth it. You should ask for an evidence hearing, present your testimony to the court. You probably won't get a dismissal of the ticket, but a reduced fine.
Both gentlemen have given you good advise. The cost of a lawyer would most likely negate any savings you might get on a reduced fine. Take a couple of photos of the roadway where the violation took place to show that with an emergency vehicle on the shoulder or partially on the shoulder did not leave room to change lanes in the event of on-coming traffic. If you can check with the Department of Transportation and get the width of the roadway, the lanes, and shoulder so there is something to go with the photos. There is a good chance with a little preparation you can either get this mitigated or amended to something else that is not as punitive.
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